357 research outputs found
Variable CW RF power coupler for 345 MHz superconducting cavities
This paper reports the development of a CW variable coupler for 345 MHz spoke-loaded superconducting (SC) cavities. The coupler inserts an 80 K copper loop into a 5 cm (2 inch) interior diameter coupling port on several types of spoke-loaded cavity operating at 2 K or 4 K. The coupling loop can be moved during operation to vary the coupling over a range of 50 dB. The coupler is designed to facilitate high-pressure water rinsing and low-particulate clean assembly. Design details and operating characteristics are discussed
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Observation of Orbitally Excited B_s Mesons
We report the first observation of two narrow resonances consistent with
states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed
as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+,
\bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1})
= 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let
Sustained virological response to treatment of chronic hepatitis C with peginterferon alfa and ribavirin
This study aimed to evaluate the rate of sustained virological response (SVR) and the clinical and treatment characteristics of patients with chronic hepatitis C (CHC). A retrospective uncontrolled cohort study was conducted among patients who received treatment for CHC between 2005 and 2008 attended at the Center for the Application and Monitoring of Injectable Medications, in Florianopolis, SC, Brazil. The inclusion criteria were: patients over 18 years of age, with a confirmed diagnosis of chronic hepatitis C according to Brazilian guidelines, treated with PEG-IFN alfa-2a or 2b associated with RBV. A total of 188 patients were included in the study: 70% men, 59% genotype 1, 27% coinfected with HIV, 31% with cirrhosis. The SVR rate, calculated by probability theory, was determined as 26% (max=57.4% and min=12.8%) and the intention to treat was 12.8%. Associations between Sustained Virological Response (SVR) and the variables sex (p=0.017), age (p=0.003), genotype (p=0.648) and cirrhosis (p=0.275), were determined in the bivariate analysis and only sex and age were significantly associated with SVR. The SVR rate was considered low, which can be partially explained by patients' unfavorable pretreatment characteristics.O objetivo do estudo foi avaliar a taxa de resposta viral sustentada (RVS) e as características clínicas e do tratamento dos pacientes portadores de hepatite C crônica. Realizou-se uma coorte retrospectiva não controlada com recorte temporal dos anos de 2005 a 2008, dos pacientes atendidos no Polo de Aplicação e Monitoramento de Medicamentos Injetáveis, em Florianópolis, SC. Os critérios de inclusão foram: pacientes maiores de 18 anos, com diagnóstico confirmado de hepatite C crônica de acordo com o protocolo brasileiro, tratados com PEG-IFN alfa-2a ou 2b associado a ribavirina. Total de 188 pacientes foi incluído no estudo, 70% homens, 59% genótipo 1, 27% co-infectados com o HIV e 31% apresentando cirrose. A taxa de RVS calculada através da teoria das probabilidades foi de 26% (max=57,4% and min=12,8%) e por intenção de tratamento de 12,8%. Verificou-se a associação da RVS com as variáveis: sexo (p=0,017), idade (p=0,003), genótipo (p=0,648) e presença de cirrose (p=0,275). Somente sexo e idade foram associados significativamente com a RVS. A taxa de RVS foi considerada baixa e, em parte, pode ser explicada pelas características desfavoráveis dos pacientes para a obtenção de RVS
Measurement of the Bs Lifetime in Fully and Partially Reconstructed Bs -> Ds- (phi pi-)X Decays in pbar-p Collisions at sqrt(s) = 1.96 TeV
We present a measurement of the Bs lifetime in fully and partially
reconstructed Bs -> Ds(phi pi)X decays in 1.3 fb-1 of pbar-p collisions at
sqrt(s) = 1.96 TeV collected by the CDF II detector at the Fermilab Tevatron.
We measure tau(Bs) = 1.518 +/- 0.041 (stat.) +/- 0.027 (syst.) ps. The ratio of
this result and the world average B0 lifetime yields tau(Bs)/tau(B0) = 0.99
+/-0.03, which is in agreement with recent theoretical predictions.Comment: submitted to Phys. Rev. Let
Observation of the structure in the Mass Spectrum in cays
The observation of the structure in decays produced in collisions at \sqrt{s}=1.96~\TeV is
reported with a statistical significance greater than 5 standard deviations. A
fit to the mass spectrum is performed assuming the presence of a
Breit-Wigner resonance. The fit yields a signal of resonance
events, and resonance mass and width of
4143.4^{+2.9}_{-3.0}(\mathrm{stat})\pm0.6(\mathrm{syst})~\MeVcc and
15.3^{+10.4}_{-6.1}(\mathrm{stat})\pm2.5(\mathrm{syst})~\MeVcc respectively.
The parameters of this resonance-like structure are consistent with values
reported from an earlier CDF analysis.Comment: 7 pages, 2 figures, submited to Phys. Rev. Let
Measurement of the ttbar Production Cross Section in ppbar collisions at sqrt s = 1.96 TeV in the All Hadronic Decay Mode
We report a measurement of the ttbar production cross section using the
CDF-II detector at the Fermilab Tevatron. The analysis is performed using 311
pb-1 of ppbar collisions at sqrt(s)=1.96 TeV. The data consist of events
selected with six or more hadronic jets with additional kinematic requirements.
At least one of these jets must be identified as a b-quark jet by the
reconstruction of a secondary vertex. The cross section is measured to be
sigma(tbart)=7.5+-2.1(stat.)+3.3-2.2(syst.)+0.5-0.4(lumi.) pb, which is
consistent with the standard model prediction.Comment: By CDF collaboratio
Search for chargino-neutralino production in ppbar collisions at sqrt(s) = 1.96 TeV
We present the results of a search for associated production of the chargino
and neutralino supersymmetric particles using up to 1.1 fb-1 of integrated
luminosity collected by the CDF II experiment at the Tevatron ppbar collider at
a center-of-mass energy of 1.96 TeV. The search is conducted by analyzing
events with a large transverse momentum imbalance and either three charged
leptons or two charged leptons of the same electric charge. The numbers of
observed events are found to be consistent with standard model expectations.
Upper limits on the production cross section are derived in different
theoretical models. In one of these models a lower limit on the mass of the
chargino is set at 129 GeV/c^2 at the 95% confidence level.Comment: To be submitted to Phys.Rev.Let
Search for charged Higgs bosons in decays of top quarks in p-pbar collisions at sqrt(s) = 1.96 TeV
7 pages, 2 figuresWe report the recent charged Higgs search in top quark decays in 2.2/fb CDF data. This is the first attempt to search for charged Higgs using fully reconstructed mass assuming H->c-sbar in small tan beta region. No evidence of a charged Higgs is observed in the CDF data, hence 95% upper limits are placed at B(t->H+b)We report on the first direct search for charged Higgs bosons decaying into cs̅ in tt̅ events produced by pp̅ collisions at √s=1.96 TeV. The search uses a data sample corresponding to an integrated luminosity of 2.2 fb-1 collected by the CDF II detector at Fermilab and looks for a resonance in the invariant mass distribution of two jets in the lepton+jets sample of tt̅ candidates. We observe no evidence of charged Higgs bosons in top quark decays. Hence, 95% upper limits on the top quark decay branching ratio are placed at B(t→H+b)< 0.1 to 0.3 for charged Higgs boson masses of 60 to 150 GeV/c2 assuming B(H+→cs̅ )=1.0. The upper limits on B(t→H+b) are also used as model-independent limits on the decay branching ratio of top quarks to generic scalar charged bosons beyond the standard model.Peer reviewe
Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events
We present a measurement of the W+W- production cross section using 184/pb of
ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the
Collider Detector at Fermilab. Using the dilepton decay channel W+W- ->
l+l-vvbar, where the charged leptons can be either electrons or muons, we find
17 candidate events compared to an expected background of 5.0+2.2-0.8 events.
The resulting W+W- production cross section measurement of sigma(ppbar -> W+W-)
= 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the
Standard Model expectation.Comment: 8 pages, 2 figures, 2 tables. To be submitted to Physical Review
Letter
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